Troubleshooting weak fire on a xj650

Hello,
I am trying to narrow down my problem of no fire or weak fire on my 650.

I am wondering if there is an easy way to power the coils and cdi module with 12 volts so I can see if it runs (bypassing a lot of the wiring and connections as well as the safety system.

I have a gremlin floating around. When the bike will run it is missing below 3,000 rpms but above that it runs better.

The plugs keep getting loaded up so I am assuming it is not getting the proper fire to burn them clean.

At this point in time it will not start. Cranks but will not fire up. Every once in a while cranking it it kicks over but will not keep running. Backfired 1 time as well.
I got this bike from a friend who gave up trying to work its problems out.

It has a new battery, several sets of spake plugs came with it as well a spare cdi module which I opened up cleaned resoldered the crappy connections.

It set up in someones garage for ~15 years befor the guy I got it from bought it. The carbs have been rebuilt, the petcock replaced, and the tank sealed. I replaced the fuse panel it was weak! Also came with an extra set of ignition coils which I rung out and tried sustituting anyway no difference.
Swapping the cdi box and the symptoms remained the same. The bike only has 3636 miles on it it is in real nice shape.


Sometimes it will run. but not at present.
Any suggestions / ideas would be greatly appreciated!
Thanks,
George

 

Honestly this sounds exactly like the problem I have, I just ordered some used coils so we'll see if that solves it.

I am thinking what if you direct wired the + feed to the coils from the battery? The ignitor just sends the signal via the ground doesnt it to the coils and then they charge and fire right? Its just an idea and I might be off on the ignitor and the way it works.

 

Hey,
I too tried a set of used coils but no help!
I rang out both sets and they were compareable.
They met the specs found in the manual.
The plug connectors on the ends of the wires were questionable so I ordered 2 sets (4) on ebay but have not received them as of yet. I understand these bikes had a lot of loose elecrtrical connections so going throught the wiring harness and cleaning and "tightening" up everything is going to be my next step. I did also buy a set of "hotter" plugs to try and burn off the "loading" they are NGK BP5ES. I also have an additional ignition module but that didn't help either.

Sometimes if I clean the plugs and get it to start it will run a while but then shortly returns to the previous condition of loading up and weak fire .
After reviewing the schematic it appears the black wire going to the cdi is a ground wire and the red/white wire is the hot. I may try disconnecting the original feeds and putting +12 to the r/w and ground out the black and see if it will start.

Bike looks real nice if I can get it to run as good as it looks I will be a happy camper!

 

Good bet since your running the wrong plugs your having issues. You should have a set of BP7ES gapped at 0.028-0.032 inches.
As for the electrical, you can bet your bottom dollar that the problem is in that rats nest, especially if the bike was left outside. Corrosion claims those things so stinkin fast... Clean every one from stem to stern and smear a little dielectric grease on the contact if you can. Packing the connector is a quick and dirty way to go but then it melts out and all over the place (icky).
Hope this helps, let us know what happens.

 

Well,
I got it running enough to get it state safety inspected and then drove it to work (45 miles each way) I talked with Rickcomatic on the phone the other night (it was gracious of him to share his valuable time with me and give me quick tutoring on tuning the carbs).
Yesterday I removed the factory breather box and installed 4 filters I got off of Ebay. I was hoping this might help to lean out the equation. I then set the air mixture screws to 2 3/4 turns from fully closed installed new plugs and took off. Running better however still rich.Had to drive it today my SSR is in the shop! Anyway I think I am on the road to recovery. I likes to run ~ 65 mph or so real good. Putting around town it still has a trend to load up. More tuning in the days ahead. What I thought to be an ignition problem looks like extremely rich idle mix!
Thanks for all the help. Will keep you posted as conditions improve. Bike has alot of power...

George

 

Hello,
Progress is slow and staedy though!
I have driven the bike ~300 miles now and for the last 3 days I have not had to change the plugs...
Still running rich!
I turned the air screws in at lunch today 1/4 turn see if that helps on the way home. I carry an extra set of plugs along in case of trouble. Bike is only getting ~ 25 miles to the gallon so I guess a lot of unburned fuel is going out the pipes. Will do some carb work this weekend. I ordered new floats and hope to have in hand by tomorrow so I can tinker this 3 day weekend.
Had a Harley looking Honda mess with me in the tunnel this morning I suprised him when I blew him away...
Thanks for all the support,
George